Unicontrolled transmitter tuning and antenna switching arrangement



March 23, 1948. J. M. DODDS 1-;T AL 2,438,116

UNI-CONTROLLED TRANSMITTER TUNING AND ANTENNA SWITCHING ARRANGEMENTS Filed Dec. 29, 1-943 /---HERIHL:$

U'N/ CONTROLLED INVENTORS JOHN MATHIESo Do 0135 AND r-m HEYwooD LIVDLIOW ATFYS.

Patented Mar. 23, 1948 STATES PATENT QFFICE UNICONTROLLED TRANSMITTER TUNING AND ANTENNA SWITCHING ARRANGE- MENT Application December 29, 1943, Serial No. 516,109 In Great Britain April 16, 1940 2 Claims.

This invention relates to radio transmitters of i the kind in which provision is made for changing expeditiously the wavelength of transmission, and it is concerned specifically with such transmitters wherein eparate aerials are used for the respective different wavelengths.

Our applications for Radio transmitters, Serial Nos. 516,103 and 516,104, and our application for Tuner, Serial No. 516,105, now Patent No. 2,420,657 granted May 20, 1947, all filed December 29, 1943, disclose various features of wave-changing transmitters and are more particularly concerned with switching arrangements whereby different inductance coils may be selectively connected with the valves.

Our application Serial No. 516,103 aforesaid describes, more particularly with reference to Fig. 9 of the drawings accompanying that specification, an arrangement wherein the several aerials are permanently connected to respective inductances which may be selectively switched to the output valve anodes.

Our application Serial No. 516,105 aforesaid describes means whereby when the switching means are moved to connect the difierent inductances selectively to a valve electrode or electrodes the setting of a tuning condenser is appropriately changed automatically.

According to the present invention there is associated with the output valve or valves of a wave-changing radio transmitter a single anode tuning inductance and a single variable condenser which is linked with a selector switch which is adapted to connect said inductance, or more usually appropriately adjusted tappings thereon, selectively to the different aerials, so that when the wavelength is changed the tuning of said inductance assumes the desired wavelength with respect to the aerial which radiates on that wavelength. The switches may be of the doublepole double-arm type adapted to be operated in unison to engage at one end of the arms pairs of fixed contacts connected to the respective aerial feeders and at the other end or the arms to engage fixed contacts connected with the tappings on the inductance, which tappings are preferably adjustable so that a suitable coupling can be provided between the inductance-condenser combination circuit and the selected aerial feeder.

The actual mechanism employed for operating the switches and the condenser may be similar to that described more particularly with reference to Fig. 6 of our above-mentioned application Serial No. 516,105. It will be appreciated that the present invention may be employed in combination with the inventions forming the subjects matter of our above-mentioned applications Serial Nos. 516,103 and 516,104.

The accompanying drawing illustrates purely diagrammatically an arrangement in accordance with the invention by way of example.

In the drawing two valves VI and V2, which are arranged in push-pull relation, have connected to their anodes the single inductance coil L across which is the variable tuning condenser C.

At Al, A2, A3, A4 are indicated four aerials for radio transmission on four difierent wavelengths, and these aerials are adapted to be selectively connected to the appropriately adjusted tappings on the inductance L by means of the double-pole double-arm switches SI and S2 which are operated in unison by the control member indicated by the dotted line B, which member is linked in accordance with and conveniently by mechanism similar to that described in the specification of aforesaid application Serial No. 516,105 to the operating member CI of the condenser C.

We claim:

1. In a radio transmitter, an output valve, tuning inductance means connected to the anode of said valve, a variable condenser forming a tuned circuit with said inductance, a plurality of aerials, means to selectively connect each one of said aerials to a respective one of a plurality of points of said inductance means, and uni-control means to operate said last-named means with and to vary said condenser.

2. In a radio transmitter, a pair of output valves, a tuning inductance connected between the anodes of said valves, a variable condenser forming a tuned circuit with said inductance,a plurality of aerials, a plurality of simultaneously operable means to selectively connect each one of said aerials to two respective ones of a plurality of points of said inductance means, and uni-control means to operate said last-named means and. to vary said condenser.

JOHN MATHIESON DODDS. JOHN HEYWOOD LUDLOW.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,649,131 Schwarz Nov. 15, 1927 FOREIGN PATENTS Number Country Date 289,875 Great Britain May 24, 1928 OTHER REFERENCES Publication, Automatic Tuning for the Amateur Transmitter, by Atkins et al. in Q. S. T. for Sept. 1940, pages 30, 31, 83. 

